un accountable (adjective) unaccountable: not explainable; mysterious
Sinonime: arcane,
astonishing, baffling,
extraordinary,
impenetrable,
incomprehensible,
inexplicable,
inscrutable,
mystic,
odd,
peculiar, puzzling,
strange,
uncommon,
unexplainable,
unfathomable, unheard-of, unintelligible, unknowable,
unusual, unwonted
Antonime: accountable,
comprehensible, explainable,
responsible